Best media for blasting engine parts?

[Screwdriver]

I use bicarbonate of soda for "sand" blasting delicate or ally bike parts.

 

[marlinspike]

I probably wouldn't bother having them done professionally as I only paid a few hundred quid for the car. It was more that we've bought a decent compressor and it seemed a shame not to use it for blasting. I might have a go with soda on some easy bits and see how I get on.